Long‐term suppression of wetland methane flux following a pulse of simulated acid rain

Wetlands are a potent source of the radiatively important gas methane (CH4). Recent findings have demonstrated that sulfate (SO42−) deposition via acid rain suppresses CH4 emissions by stimulating competitive exclusion of methanogens by sulfate‐reducing microbial populations. Here we report data from a field experiment showing that a finite pulse of simulated acid rain SO42− deposition, as would be expected from a large Icelandic volcanic eruption, continues to suppress CH4 emissions from wetlands long after the pollution event has ceased. Our analysis of the stoichiometries suggests that 5 years is a minimum CH4 emission recovery period, with 10 years being a reasonable upper limit. Our findings highlight the long‐term impact of acid rain on biospheric output of CH4 which, for discrete polluting events such as volcanic eruptions, outlives the relatively short‐term SO42− aerosol radiative cooling effect